Style.css & Comment Errors

Hey guys,
On my website
https://stantheman.uk.to/

When i click on “the comments” show comment it shows this error:

Related Posts
Fatal error: Call to undefined function similar_posts() in /home/stanley/public_html/wp-content/themes/seaview/single.php on line 74

Anyone know what the problem could be? or how to fix it?

Also how to edit the description tag usually found on top of a wordpress blog, its font type, like from Arial to Verdana or something, i looked for it in the style.css but its giving no clues to what it could be

my style.css

/*
Theme Name:Sea View
Theme URI: https://www.themespack.com/
Description: WordPress Theme  Sea View  by <a href="https://www.themespack.com/">Themespack</a>.

Author: wonder
Author URI: https://www.themespack.com/

	This theme was designed and built by WP Theme
                The CSS, XHTML and design is released under GPL
                https://www.opensource.org/licenses/gpl-license.php

*/
body {
	font: 75%/150% Verdana, Arial, Helvetica, sans-serif;
 	color: #2c2c2c;
	background: #f3e9d2 ;
	margin: 0px;
	padding: 25px 0px 10px 0px;
}
a {
	color: #e1b576;
	text-decoration: none;
}
a:visited {
	color: #e1b576;
	text-decoration: none;
}
a:hover {
	color: #000000;
	text-decoration: none;
}
img {
	border: none;
}
p {
	padding: 0px 0px 15px;
	margin: 0px;
}
h1 {
	margin:0px;

	padding-left: 0px;
	height: 60px;
	font: bold 36px/100% "Trebuchet MS", Verdana, Bell MT;
	color: #ffffff;
}
h1 a, h1 a:visited{
	color: #ffffff;
	text-decoration: none;
}
h1 a:hover{
	color: #ffffff;
	text-decoration: none;
}
h2 {
	color: #043E01;
	margin: 0px 0px 2px;
	border-bottom: 1px dotted #DFD266;
    font-size:12px;
	font-family:Verdana, Arial, Helvetica, sans-serif;
	padding-bottom: 3px;
}
h2 a, h2 a:visited {
	color: #043E01;
	text-decoration: none;
}
h2 a:hover {
	color: #043E01;
	text-decoration: none;
}
h3 {
	color: #043E01;
	font-size:12px;
	font-family:Verdana, Arial, Helvetica, sans-serif;
	margin: 10px 0px 5px;
	border-bottom : 1px dotted #DFD266;

}
h4 {
	color: #043E01;
	font-size:12px;
	font-family:Verdana, Arial, Helvetica, sans-serif;
	margin: 10px 0px 5px;
	border-bottom : 1px dotted #DFD266;

}
form {
	margin:0px;
	padding:0px;
}
#page {
	margin: 0px auto;
	width: 900px;
	border-top: 10px solid #183000;
	background: #FFFFFF ;
}
/* header area */
#header {
	background: #f3e9d2 url(img/header.jpg) no-repeat;
	height: 250px;
	position: relative;
}
#headerlogo {
	position: relative;
	padding: 20px 0px 0px 35px;
	height: 60px;
}
#headerlogo .description{
	position: absolute;
	left: 45px;
	bottom: 3px;
	color: #ffffff;
	font-size: 16px;
}
#nav {
	list-style: none;
	margin: 0px;
	position: absolute;
	left: 0px;
	top: -28px;

}
#nav li {
	float: left;
	margin-left: 5px;
}
#nav .current_page_item a, #nav .current_page_item a:visited{
	color: #475404;
	text-decoration: none;
}
#nav .page_item a{
	color: #475404;
	text-decoration: none;
	background: #F3E9D2 ;
	padding: 5px 15px;
	font: bold 14px/100% Verdana, Helvetica, sans-serif;
	border-top: 1px solid #043b4a;
	border-left: 1px solid #043b4a;
	border-right: 1px solid #043b4a;
	display: block;
}
#nav .page_item a:hover {
	color: #000000;
}
#navads
{
background: #043b4a ;
height: 15px;
}

#navbottom
{
background: #ffffff url(img/bottom-nav.gif) repeat-x;
height: 14px;
margin-bottom: 1.5em;
}

/* content  */
#content {
	padding: 0px 10px 25px 13px;
	float: right;
	width: 630px;
	overflow: hidden;
}
.post {
	clear:both;
	padding-top: 15px;
}
.entry {
	float:left;
	width: 620px;
}
.post-cat {
    padding-left: 5px;
	float:left;
	font-size: 95%;
	color: #53544E;
}
.post-comments {
	padding-left: 5px;
	float: right;
	font-size: 95%;
}
.post-calendar {
	padding-left:5px;
	float: right;
	font-size: 95%;
	color: #53544E;
}
.postmetadata {
	color: #000000;
	font-size:12px;
	padding:8px;
	background: #ffffff  url(img/meta.jpg) repeat-x;
	height:18px;
}
.postmetadatap {
	color: #000000;
	font-size:14px;
	padding:8px;
	background: #ffffff  url(img/pback.jpg) repeat-x;
	height:60px;
}
.postrss{
	color: #000000;
	font-size:13px;
	padding: 3mm;
	border: thin dotted #2c2c2c;
	font: verdana;
}
.googleads{
	width:615px;
	float:left;
	color:#666;
	background:#fff;
	margin:5px 0 5px 0px;
	padding:10px 0 10px 20px;
	border: 1px solid #eee;
}
.similiar{
	width:595px;
	float:left;
	color:#000000;
	text-align:justify;
	margin:5px auto;
	padding:5px 6px 10px;
}
.post-views {
	padding-left:5px;
	float: left;
	font-size: 95%;
	color: #53544E;
}
.post-content {
	clear: both;
	padding-top: 10px;
}
.navigation {
	clear: both;
	padding: 10px 0px;
}
.navigation a, .navigation a:visited {
	color: #53544E;
}
.previous-entries a {
	float: left;
	padding-left: 5px;
}
.next-entries a {
	float: right;
	padding-right: 5px;
}

/* comments  */
#comments, #respond {
	border-bottom: 1px dotted #DFD266;
	padding: 10px 0 5px 0;
	clear: both;
}
.commentlist {
	margin: 10px 0px;
	padding-left: 20px;
	line-height: 130%;
}
.commentlist li{
	padding: 5px 10px;
}
.commentlist .alt {
	background: #ffffff;
	border: 1px dotted #EBEFE4;
}
.commentlist cite, .commentlist cite a, .commentlist cite a:visited {
	font-weight: bold;
	font-style: normal;
	font-size: 120%;
	color: #183000;
}
.commentlist small {
	margin-bottom: 5px;
	display: block;
	font-size: 87%;
}
#commentform {
	margin-top: 10px;
	font: 110% Arial, Helvetica, sans-serif;
}
#commentform p {
	padding: 6px 0px;
	margin: 0px;
}
#commentform label{
	color: #242121;
	font-size: 87%;
}
#commentform input{
	width: 200px;
	background:#ffffff;
	border: 1px solid #EBEFE4;
	padding: 3px;
	margin-top: 3px;
}
#commentform textarea{
	width: 515px;
	height: 115px;
	background:#ffffff;
	border: 1px solid #EBEFE4;
	padding: 2px;
	margin-top: 3px;
}
#commentform textarea:focus, #commentform input[type="text"]:focus {
	background: #ffffff;
}
#commentform #submit{
	background: #ffffff ;
	font: bold 12px Arial, Helvetica, sans-serif;
	color: #183000;
	border:1px solid #053743;
    float:left;
	width: 144px;
	height: 28px;
	cursor: pointer;
}
/*sidebar */
#sidebar {
    padding: 10px 0px 20px 13px;
	float: left;
	width: 200px;
	color: #ffffff;
	overflow: hidden;

}

/*sidebar title  */
#sidebar h2 #sidebar .sidebartitle{
	font-size:12px;
	font-family:Verdana, Arial, Helvetica, sans-serif;
	color: #4F9DB0;
	margin: 20px 0px 2px;
	border-bottom: 1px solid #CAC73C;
}
/*sidebar text styles */
#sidebar a, #sidebar a:visited{
	color: #183000;
	text-decoration: none;
}
#sidebar a:hover{
	color: #183000;
	text-decoration: none;

}
/*sidebar list level1 */
#sidebar ul {
	margin: 0;
	padding: 0;
}
#sidebar ul li {
	list-style: none;
	margin: 0;
	padding: 0;
	border: none;
}
/*sidebar list level2 */
#sidebar ul li ul {
	padding: 0;
	margin: 0;
}
#sidebar ul li ul li{
	padding: 2px 0 2px 0px;
	border-bottom: 1px solid #EBEFE4;
}
/*sidebar list level3 */
#sidebar ul li ul li ul li{
	padding: 1px 0 1px 10px;
	border: none;
}
/*blogroll */
ul.list-blogroll li{
	padding-left: 5px !important;
}
/*meta */
ul.list-meta li{
	padding-left: 5px !important;
}
/*rss */
ul.list-rss li{
    padding-left: 5px !important;
}

/*category bar */
ul.list-cat li, li.bar_categories li{
	padding-left: 5px !important;
}
/*recent bar  */
ul.list-rec li, li.bar_comments ul li {
	padding-left: 5px !important;
}
/*archives bar */
ul.list-archives li, li.bar_archives li{
	padding-left: 5px !important;
}
/*pages bar */
ul.list-page li, li.bar_pages li, li.bar_recent_entries li{
	padding-left: 5px !important;
}
/*sub-pages bar */
ul.list-page li ul li, li.bar_pages li ul li{
	padding-left: 10px !important;
}
/*calendar bar  */
li.bar_calendar td {
	padding: 1px 7px;
}
/*text bar */
.textbar {
	padding-top: 5px;
}

/*search form */
#searchform {
	margin: 15px 0 0;
}
#searchform br {
	display: none;
}
#searchform #s {
	border:1px solid #183000;
	width: 115px;
	height: 22px;
	padding: 4px 5px 0px 5px;
	border: 1px solid #043b4a;
	background: #ffffff;
	margin-right: 2px;
	color: #000000;
	font-weight: normal;
}
/* search form button - to specify button only use input[type="submit"] */
#searchform input {
	background:#ffffff ;
	border: 1px solid #183000;
	width: 65px;
	height: 28px;
    font: bold 12px Arial, Helvetica, sans-serif;
	color: #183000;
	vertical-align: middle;
}

/* page close */
#close {
	clear: both;
	background: #ffffff;
    color: #ffffff;
	font-size: 95%;
	line-height: 130%;
	padding-bottom: 10px;
}

/* footer bar */
#footer {
	margin: 0px auto;
    width: 900px;
    color: #ffffff;
    height: 30px;
    font-size: 12px;
	line-height: 100%;
    background: #183000 ;

}
#footer a, #credit a:visited {
    margin-top: 8px;
	color: #ffffff;
}
/* alignments */
.center {
	text-align: center;
}
img.center, img[align="center"] {
	display: block;
	margin-left: auto;
	margin-right: auto;
}
.alignleft {
	float: left;
}
img.alignleft, img[align="left"] {
	float:left;
	margin: 2px 10px 5px 0px;
}
.alignright {
	float: right;
}
img.alignright, img[align="right"] {
	float:right;
	margin: 2px 0px 5px 10px;
}
.clear {
	clear:both;
}
hr.clear {
	clear:both;
	visibility: hidden;
	margin: 0px;
	padding: 0px;
}

—————Then this corresponds with the header.php file:——————-

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml">

<head profile="https://gmpg.org/xfn/11">
<meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php bloginfo('charset'); ?>" />

<title><?php bloginfo('name'); ?> <?php if ( is_single() ) { ?> &raquo; Blog Archive <?php } ?> <?php wp_title(); ?></title>

<meta name="generator" content="WordPress <?php bloginfo('version'); ?>" /> <!-- leave this for stats -->

<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); ?>" type="text/css" media="screen" />
<link rel="stylesheet" href="<?php bloginfo('stylesheet_directory'); ?>/print.css" type="text/css" media="print" />
<link rel="alternate" type="application/rss+xml" title="<?php bloginfo('name'); ?> RSS Feed" href="<?php bloginfo('rss2_url'); ?>" />
<link rel="pingback" href="<?php bloginfo('pingback_url'); ?>" />

<?php wp_head(); ?>
</head>
<body>
<div id="page">
  <div id="header">
    <div id="headerlogo">
	  <h1><a href="<?php echo get_settings('home'); ?>/"><?php bloginfo('name'); ?></a></h1>
	  <div class="description"><?php bloginfo('description'); ?></div>
	</div>
	<ul id="nav">
	  <li class="page_item"><a href="<?php echo get_settings('home'); ?>/" title="Home">Home</a></li>
	  <?php wp_list_pages('sort_column=menu_order&depth=1&title_li=');?>
</ul>
</div>
<div id="navbottom"></div>
  <!--/header -->